1. Field of the Invention
This invention generally relates to an automobile shock absorber with frequency-selective damping action. In general, such a shock absorber might typically have a working cylinder filled with damping fluid, which working cylinder can be divided into two working chambers by a piston. The piston can preferably have throttle valves for controlling flow of fluid between the two working chambers, thereby creating a damping action. The piston can preferably be fastened to a piston rod, and the piston rod can have a fastening device for fastening the piston rod to a portion of the automobile, i.e. the wheel suspension. In addition, the working cylinder can also have a fastening device for mounting the shock absorber to a portion of the automobile, such as the vehicle frame, thereby creating a damping action between the wheel and the frame.
2. Background Information
Some types of shock absorbers having a frequency-selective action are known, such as the shock absorber disclosed by German Laid Open Patent Appln. No. DE-OS 40 29 596. With the shock absorber disclosed thereby, it is possible to provide strong damping in a mechanical manner for the two characteristic natural frequencies of the vehicle body and the vehicle wheels. However, to achieve this damping, single-mass resonators, or oscillators, are provided both in the hollow piston rod and also in a bypass line located parallel to the outer cylinder of the shock absorber. These single-mass resonators each consist of an axially-movable inertial body with elastic connections fastened thereto. The inertial bodies, both in their rest positions and when they make short excursions, allow the flow of fluid from the upper working chamber to the lower working chamber, and block the flow of fluid as soon as they vibrate in resonance. The resonance frequencies of the systems of inertial bodies are tuned to the natural frequencies of the vehicle.
Another type of shock absorber to damp movements is disclosed by German Laid Open Patent Appln. No. 40 24 966, which corresponds to U.S. Pat. No. 5,265,704, in which a dynamic wheel load can be reduced by intervention in the damping element by means of a frequency-dependent increase of the passive stiffness of the suspension element, to modify the dynamic wheel loads in the sense of a reduction.